Repository navigation
Encoding of CSS files #1628
Description
CSS files in an EPUB package MUST be encoded in UTF-8 or UTF-16. The i18n WG supports the idea of using UTF-8 only. Why is UTF-16 mentioned here?
CSS files in an EPUB package MUST be encoded in UTF-8 or UTF-16. The i18n WG supports the idea of using UTF-8 only. Why is UTF-16 mentioned here?
Activity
mattgarrish commentedon Apr 12, 2021
There was a discussion about dropping UTF-16 in #50
It was also reconfirmed for CSS in a telecon discussion (the referenced thread in google groups appears to be lost to time now, though)
The only concern I'd have with making a change is whether we risk breaking existing content. Maybe we should just advise against the use rather than disallow it?
iherman commentedon Apr 12, 2021
I had the same concern...
iherman commentedon Apr 17, 2021
@xfq @mattgarrish would it be possible to change the text as follows:
from
to
@xfq please follow the link to deprecated to see what it means in the context of EPUB 3.3
However, I see UTF-16 mentioned in two more places in the document:
I believe the media type registration must stay, because it is "legal" to use UTF-16 (because it is just deprecated). I would think, however, that the same change should be made on the XML case as for CSS.
WDYT?
cc @dauwhe @wareid @shiestyle
mattgarrish commentedon Apr 21, 2021
Isn't this a bit of a contradiction? If it must be encoded in utf-8, then that negates using utf-16 at all.
This is kind of an oddball case since we're only deprecating half the requirement.
If we go this route, maybe it might make more sense to phrase it along the lines of: "It MUST be encoded in UTF-8 or UTF-16, but the use of UTF-16 is now deprecated."
That would be consistent with not invalidating any utf-16 content that might be out there while recommending it no longer be used.
iherman commentedon Apr 22, 2021
You are right. Let us go this way if we get the blessing of the WG (on the call tomorrow)
mattgarrish commentedon Apr 22, 2021
It appears the general web direction is to use utf-8 exclusively, so a broader recommendation against using utf-8 for xml, too, seem in keeping with that trend.
The Encoding spec says this:
UTF-16 is now considered a legacy encoding format.
It also appears that only a fraction of a percent of web content uses it (although that's not necessarily a good barometer of publishing use).
dauwhe commentedon Apr 23, 2021
Just for reference... CSS says stylesheets should be UTF-8
iherman commentedon Apr 23, 2021
The issue was discussed in a meeting on 2021-04-23
List of resolutions:
View the transcript
1.1. CSS files encoding
See github issue #1628.
See github pull request #1645.
Dave Cramer: first, encoding of CSS files
… we say CSS files must be encoded in UTF8 or UTF16
… web is leaning towards UTF8 for everything
… i18n WG suggests we use UTF8 for everything
… but some existing epubs might already use UTF16
… proposal would deprecate UTF16 CSS files
… issue is the epubcheck would be obligated to display warning if it found UTF16 CSS
… not sure how big of a thing this is
… CSS WG has recommended UTF16 in past
… i'm okay with deprecating UTF16
… the proposed phrasing is in the issue
Ivan Herman: not sure how much books currently use UTF16, but epubcheck having to warn about this means that some changes will have to be made to epubcheck
… but this isn't too big an obstacle
… there is already a PR
… ready to go
… it keeps the current sentence but adds "but UTF16 is deprecated"
… also, the exact same thing is happening in the spec for XML char encoding
… so the PR makes the conforming change to XML too
Matt Garrish: i'm not sure how much epubcheck even looks at CSS
… we've talked about deprecating UTF16 before, but we opted to keep it at the time for backwards compatibility reasons
Brady Duga: are there enough positive benefits to go ahead with this?
… also, deprecation feels like it should be a statement of intent (i.e. that we will remove in future), but the truth is that we intend to keep this compatibility forever
Dave Cramer: we're trying to work with i18n WG
Brady Duga: is it deprecated in CSS?
Dave Cramer: they say you SHOULD use UTF8
Brady Duga: i would say "you should use UTF8", but i'm not sure about deprecating UTF16
Ivan Herman: i suspect there are tools and scripts which simply do not work with UTF16
… so we minimize the chance of people trying to use UTF16 CSS epubs with these tools
Brady Duga: i'd be surprised if there are a lot of tools out there that don't support both encodings
Matt Garrish: we are trying to align with the web, and what the other specs are saying
… i.e. guiding people towards only using UTF8
Dave Cramer: i understand the concerns with deprecation
… we could say CSS must be either UTF8 or UTF16, but it should be UTF8
Matt Garrish: that puts us more or less back in the same place, there's going to be an epubcheck warning
Dave Cramer: and then people also have to go look up the definition of "deprecated", so maybe not saying that is more straightforward
Ivan Herman: for sake of argument, Rust for example, which is gaining popularity, only uses UTF8
Ivan Herman: but yes, let's change the PR